Multiple UV mapping problem
Example : we have a plane and want to 3 materials based on two textures.

Plane parts :


The cockpit : glossy material with texture 1
The nose : diffuse material also with texture 1
The other parts : diffuse material with texture 2





Create your plane
Add the three materials
In edit mode, select the wanted faces and assign them to the corresponding material





Create your UV seams (probably corresponding to the material). You may also have done the seams before the material assignation





Select the wanted parts using the "select" button of the material,
Then UV unwrap





The materials can be defined as you wish (here I used a bake to produce the textures
You can also export the UV map parts separately in order to paint over it in the tool you want (or paint directly here in Blender)